BACKGROUND:Balantidium coli, a ciliated protozoan parasite that infects primates and pigs, and is the largest protozoan to infect humans, is a well-known cause of diarrhoea and dysentery in humans. Extra-intestinal disease is uncommon, however. OBJECTIVE: We describe a case of lung involvement, with severe pulmonary haemorrhage resulting in iron deficiency anaemia and respiratory failure, of a 20-year-old, immune-competent man. RESULTS: Diagnosis was made by bronchial biopsy and lavage, which showed numerous trophozoites compatible with B. coli with a background of acute inflammatory cells. The origin of infection was not clear, but inhalation of pig manure was postulated as there was no history of intestinal disease. The patient was treated with oxytetracyline and metronidazole, kept in an ICU, improved within 48 hours, and was discharged within 4 days. CONCLUSION:B. coli infection should be considered as part of the differential diagnosis of pulmonary haemorrhage.